Pollination and Fertilization 



171 



combination of A with A, A with B, or B with B so 



that A will appear on an average three times as often as B. 



In succeeding generations A 



crossed with A, or B crossed 



with B, will " breed-true " 



to A or B, but AB plants, 



or hybrids, will continue to 



separate out in the same 



proportion as before. 



Since so much has been 

 learned about flowers and 

 their insect guests, it has 

 been asked whether flowers 

 were designed to attract 

 insects or whether insects,- 

 by visiting flowers, have 

 given them their markings 



where they have come in contact with them, and so have 

 made them irregular by always lighting on the same spot. 1 

 We can tell what was in the past only by thinking about what 

 we see now. At least, we feel sure, from fossil plants and 

 insects, that there were no showy flowers until bees and butter- 

 flies had been created to gather honey. 



Dr. Kolbe was one morning the uninvited guest at a sugar- 

 bird's breakfast. We will " let him tell in his own words " his 

 thoughts on that occasion. 



"THE GLADIOLUS AND THE SUGAR-BIRD. 



"Some time ago I was reading ' The Making of Flowers,' 

 by the Rev. Prof. G. Henslow (" Romance of Science Series," 

 S.P.C.K.), in which he explains the forms and markings of 

 flowers as a result of plant responsiveness to the mechanical 

 stimulus of insects in search of honey. The theory was parti- 

 cularly attractive to me : it seemed to explain so much. Thus 

 thinking, I noted one day how a lot of Gladioli in a garden 



1 That flowers and insects have developed independently of one 

 another ; s a third possibility. 



